---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/21405#article
headline: "21405: Cannot set VoiceFallbackUrl without setting Url"
url: https://www.twilio.com/docs/api/errors/21405
inLanguage: en
dateModified: 2025-12-18T21:40:49.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 21405: Cannot set VoiceFallbackUrl without setting Url

Log Level: ERROR

## Description

You cannot set a fallback URL without specifying a primary URL